Retention of polyphenols in blueberries (Vaccinium corymbosum) after different cooking methods, using UHPLC-DAD-MS based metabolomics

This study investigated the impacts of baking, boiling and microwaving methods on polyphenols in blueberries, using ultra-high performance liquid chromatography (UHPLC) with a photodiode array detector (PDA) and mass spectrometer (MS). Twenty-eight characteristic peaks were found in blueberries of which 25 were significantly affected by cooking. The retention of each compound was calculated based on its peak areas in PDA chromatograms and expressed as ratio (%) of its peak area in cooked to fresh blueberries. The retention of total anthocyanins ranged from 74.3-76.4%, 52.9-77.4%, and 58.0-72.3%, and the values for other polyphenols ranged from 77.1-88.7%, 76.0-86.7%, 66.6-76.8%, respectively, after baking, boiling, and microwaving treatments. Caffeoylquinic acid was the predominant peak in both cooked and fresh blueberries. Its concentrations in blueberries baked for 5 min or boiled for 1, 3, and 10 min were not significantly different from those in fresh samples (p > 0.05). An A-type procyanidin trimer was found to be the most unstable polyphenol; its concentrations decreased to 53.0%, 42.8%, and 36.1% of that in fresh blueberries, respectively, after 15-min baking, 10-min boiling, and 45-s microwaving. Compared to other polyphenols, caffeoylquinic acid, catechin and quercetin glycosides were the most stable. In general, microwaving led to the highest losses of polyphenols when cooking blueberries.